It is known that levulinic acid or its esters can be converted into gamma-valerolactone (γ-valerolactone)
by catalytic hydrogenation. The conversion may proceed via hydrogenation to 4-hydroxy pentanoic acid followed by (trans)esterification to γ-valerolactone or via (trans)esterification of the enol form of levulinic acid to Angelica lactone followed by hydrogenation to γ-valerolactone. γ-valerolactone may be further hydrogenated, via 1,4-pentadiol, into methyl tetrahydrofuran (MTHF). Processes for the conversion of levulinic acid into γ-valerolactone are for example disclosed in U.S. Pat. No. 5,883,266, WO 02/074760 and WO 98/26869. A process for the catalytic hydrogenation of levulinate esters to form γ-valerolactone is disclosed in EP 069 409 A1.
γ-valerolactone is known to be a very stable compound that is, starting from levulinic acid or its esters, more easily formed under catalytic hydrogenating conditions than non-cyclic hydrogenated compounds such as pentanoic acid or pentanoates. Due to its high stability, it is difficult to convert the thus-formed γ-valerolactone into pentanoic acid or a pentanoate. In general, it is difficult to open 5- or 6-membered lactone rings, in particular 5-membered lactone rings.
There is a need for a process for the hydrogenation of γ-valerolactone, levulinic acid or its esters into pentanoic acid or pentanoates in sufficiently high yield. Such pentanoates could be advantageously used as bio-derived compounds in transportation fuels in particular diesel fuel.